Exhaust gas recirculation type combined plant

ABSTRACT

Widening a partial load operation range of an exhaust gas recovery type combined cycle plant in which a gas turbine and steam turbine are combined and further improving heat efficiency.  
     Suppressing a temperature of internal gas in the compressor when recirculating gas turbine exhaust gas at partial load operation time and then returning to the compressor so as to increase exhaust gas recirculation amount. The partial load operation range can be widened and further the heat efficiency can be improved.

BACKGROUND OF THE INVENTION

1. 1. Field of the Invention

2. This invention relates to a gas turbine apparatus, and moreparticularly to a exhaust gas recirculating type combined cycle plantwherein exhaust gas is recirculated to an air intake side of acompressor.

3. 2. Description of Related Art

4. Japanese Unexamined Patent Application No. Hei7-34900 has disclosedan exhaust gas recirculating type combined plant wherein a part ofexhaust gas from a gas turbine is returned to an air intake of acompressor so as to raise a compressor air intake temperature so that acombustion temperature at the time of partial loading or gas turbineexhaust gas temperature is prevented from dropping thereby preventing adrop in cycle heat efficiency at the time of the partial loading.

5. Further, according to Japanese Unexamined Patent Application No.Sho56-141040, before recirculated combustion gas enters a compressor,water is sprayed so that it is vaporized. A cooling unit is provided ona compression air path out or the compressor and by supplying coolantmedium, heat is recovered so that a rate of heat recovery from exhaustgas is improved.

6. However, the Japanese Unexamined Patent Application No. Hei7-34900has not disclosed anything about widening a range in which highefficiency partial load operation is enabled by stabilized recirculationof exhaust gas. Further, Japanese Unexamined Patent Application No.Sho56-141040 has not mentioned anything about the partial loadoperation.

7. The combined cycle plant has such a feature that there exists anatmospheric temperature maximizing its plant efficiency and the plantefficiency drops at other temperatures than the atmospheric temperature.

SUMMARY OF THE INVENTION

8. An object of the present invention is to provide an exhaust gasrecirculation type gas turbine apparatus having a wide partial loadoperation range allowing high efficiency operation.

9. Another object of the present invention is to provide an exhaust gasrecirculation type gas turbine apparatus capable of obtaining a desiredoutput efficiently even when the external temperature changes.

10. To solve the aforementioned problem, the first invention provides anexhaust gas recirculation type gas turbine apparatus comprising: acompressor for compressing air; a combustion chamber for burningcompression air exhausted from the compressor and fuel; a gas turbinedriver by gas turbine exhaust gas from the combustion chamber; arecirculation path for recirculating a part of the gas turbine exhaustgas to an intake of the compressor; a recirculation amount control unitfor adjusting an amount of gas turbine exhaust gas to be returned to theintake of the compressor corresponding to a change in load of the gasturbine; and a spray unit for introducing liquid droplets into aninterior of the compressor in which mixing gas comprising gas turbineexhaust gas passing through the recirculation path and air flows so asto vaporize the introduced liquid droplet during a flow in thecompressor.

11. As a result, air is compressed in the compressor, the compressed airand fuel are burned in the combustion chamber, the gas turbine is drivenwith gas turbine exhaust gas from the combustion chamber, a part of thegas turbine exhaust gas is recirculated to the intake of the compressorthrough the recirculation path, the amount of the gas turbine exhaustgas to be returned to the intake of the compressor is adjustedcorresponding to a change in the load of the gas turbine, and sprayingliquid droplets from the spray unit so as to introduce the liquiddroplets into the compressor in which mixing gas comprising gas turbineexhaust gas passing through said recirculation path and air flows sothat the introduced liquid droplets are vaporized during a flow in thecompressor.

12. Because of vaporizing the liquid droplets in the compressor, a riseof the compressor exit temperature is suppressed so that the temperatureof the mixing gas entering the compressor is raised, the recirculationamount can be increased and further the heat efficiency in thecompressor can be improved. As a result, the partial load operationrange in which the compressor can be operated efficiently can bewidened.

13. According to an embodiment of the present invention, the gas turbineexhaust gas recirculation type gas turbine apparatus comprises: acompressor for compressing air; a combustion chamber for burningcompression air exhausted from the compressor and fuel; a gas turbinedriven by gas turbine exhaust gas from the combustion chamber; arecirculation path for recirculating a part of the gas turbine exhaustgas to an intake of the compressor; a recirculation amount control unitfor adjusting an amount of gas turbine exhaust gas to be returned to theintake of the compressor corresponding to a change in load of the gasturbine; and a spray unit for spraying liquid droplets over air suppliedto the compressor and gas turbine exhaust gas passing through saidrecirculation path so as to introduce the liquid droplets into thecompressor in which the air and the gas turbine exhaust gas flow so thatthe introduced liquid droplets are vaporized during a flow in saidcompressor. As a result, in addition to the aforementioned matter, it ispossible to vaporize the liquid droplets at a relative upstream in thecompressor so that the temperature in the compressor can be continuouslychanged.

14. While suppressing a rise of the compressor exit temperature byvaporizing the liquid droplets in the compressor, the temperature of themixing gas entering the compressor can be raised, resulting in theincrease of the recirculation amount. Further, the improvement of theheat efficiency in the compressor allows the partial load operationrange allowing a high efficiency operation of the compressor to bewidened.

15. The second invention provides an exhaust gas recirculation type gasturbine apparatus comprising: a compressor for compressing air; acombustion chamber for burning compression air exhausted from thecompressor and fuel; a gas turbine driven by gas turbine exhaust gasfrom the combustion chamber; a recirculation path for recirculating apart of the gas turbine exhaust gas to an intake of the compressor; arecirculation amount control unit for adjusting an amount of gas turbineexhaust gas to be returned to the intake of the compressor correspondingto a change in load of the gas turbine; a spray unit for introducingliquid droplets into an interior of the compressor in which mixing gascomprising gas turbine exhaust gas passing through the recirculationpath and air flows so as to vaporize the introduced liquid dropletduring a flow in said compressor; and a spray amount control unit forcontrolling a spray amount of the liquid droplets corresponding to therecirculation amount.

16. While suppressing a rise of the compressor exit temperature byvaporizing the liquid droplets in the compressor, the temperature of themixing gas entering the compressor can be raised, resulting in theincrease of the recirculation amount. Further, because the heatefficiency in the compressor can be improved, the partial load operationrange allowing a high efficiency operation of the compressor can bewidened.

17. The compressor intake temperature and exit temperature change aredepended on the recirculation amount, and thereby the spray amount canbe appropriately adjusted.

18. As a result, by spraying the liquid droplets to intake airintroduced into the compressor on demand by means of a simple apparatussuitable for actual purpose so that the introduced liquid droplets arevaporized in the compressor, the widening of the partial load operationrange and improvement of the efficiency of the combined cycle plant canbe achieved.

19. The third invention provides an exhaust gas recirculation type gasturbine apparatus comprising: a compressor for compressing air; acombustion chamber for burning compression air exhausted from thecompressor and fuel; a gas turbine driven by gas turbine exhaust gasfrom the combustion chamber; a recirculation path for recirculating apart of the gas turbine exhaust gas to an intake of the compressor; aspray unit for introducing liquid droplets into an interior of thecompressor in which mixing gas comprising gas turbine exhaust gaspassing through the recirculation path and air flows so as to vaporizethe introduced liquid droplet during a flow in the compressor; atemperature detector for detecting a temperature of air supplied to thecompressor; and a control unit for controlling so that in the case of afirst temperature region in which the detected temperature is set, therecirculation is executed and spray of droplets from the spray unit isstopped, in the case of a second temperature region which is higher thanthe first temperature region, the recirculation is executed and thespray of droplets from the spray unit is executed and in the case of athird temperature region which is higher than the second temperatureregion, the recirculation is stopped and the spray of droplets from thespray unit is executed.

20. This will easily provide a desired load efficiently regardless ofthe change of external temperature.

21. An exhaust gas recirculation type gas turbine apparatus is preferredto comprise a control unit for controlling a spray amount of dropletfrom said spray unit depending on a humidity of air supplied to thecompressor.

22. In place of the third invention's control unit, the fourth inventionprovides an exhaust gas recirculation type gas turbine apparatuscomprising: a control unit for controlling so that in the case of afirst temperature region in which the detected temperature is set, therecirculation is executed and spray of droplets from the spray unit isstopped, in the case of a second temperature region which is higher thanthe first temperature region, the recirculation is stopped and the sprayof droplets from the spray unit is stopped and in the case of a thirdtemperature region which is higher than the second temperature region,said recirculation is stopped and the spray of droplets from the sprayunit is executed.

23. This will easily provide a desired output efficiently regardless ofthe change of the external temperature.

24. An exhaust gas recirculation type gas turbine apparatus is preferredto comprise a control unit for controlling a spray amount of dropletfrom said spray unit depending on a humidity of air supplied to thecompressor.

25. An exhaust gas recirculation type gas turbine apparatus according toclaim 1 further comprising a control unit for controlling a spray amountof droplet from said spray unit depending on a humidity of air suppliedto the compressor.

26. According to a fifth aspect of the invention, there is provided anexhaust gas recirculation type gas turbine apparatus comprising: acompressor for compressing air; a gas turbine chamber for burningcompression air exhausted from the compressor and fuel; a gas turbinedriven by gas turbine exhaust gas from the gas turbine chamber; arecirculation path for recirculating a part of the gas turbine exhaustgas to an intake of the compressor; and a carbon dioxide gas removingunit installed in a flow path of gas turbine exhaust gas for reducingthe concentration of carbon dioxide gas in the gas turbine exhaust gasdischarged after air containing the recirculated exhaust gas isintroduced to the gas turbine chamber.

27. As a result, carbon dioxide (e.g., CO₂) can be removed effectivelywhile achieving a high efficiency operation. Further, the size of thecarbon dioxide removing unit can be reduced. Because the pressure lossof the gas turbine exhaust path can be reduced by the miniaturization,the efficiency drop during the gas turbine operation can be suppressedthereby contributing to the high efficiency operation.

28. The carbon dioxide gas removing measure can be disposed between adiverging portion of the recirculation path of the gas turbine exhaustgas path and an emitting portion for emitting the gas turbine exhaustgas. As a result, the gas turbine exhaust gas containing highconcentration carbon dioxide gas can be removed, so that the carbondioxide gas removing efficiency can be maintained at a high level inaddition to the aforementioned effect. Further, because the pressureloss can be further reduced, the high efficiency operation is enhanced.

29. Or the carbon dioxide gas removing measure can be disposed betweenthe gas turbine of the gas turbine exhaust gas path and the divergingportion of the recirculation path. As a result, a large amount of thegas turbine exhaust gas can be supplied so that the carbon dioxide gasremoving efficiency can be maintained at a high level in addition to theaforementioned effect.

30. Of the carbon dioxide gas removing measure can be disposed on therecirculation path. As a result, the carbon dioxide gas removing unitcan be installed easily. Further, the maintenance work for this unit isfacilitated. Further, the pressure loss at a discharge portion ofexhaust gas to the air car be reduced, the efficiency drop of the gasturbine can be further suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

31. Other features and advantages of the invention will be apparent fromthe following description taken in connection with the accompanyingdrawing wherein:

32.FIG. 1 is a schematic diagram of an embodiment of the presentinvention;

33.FIG. 2 is a schematic diagram for explaining a control of anintegrated control apparatus;

34.FIG. 3 is a diagram showing fluid behavior in the vicinity of a vanein the compressor;

35.FIG. 4 is a diagram showing a change in incidence in the compressordue to water spray;

36.FIG. 5 is a diagram showing a relation between the recirculation rateand spray rate;

37.FIG. 6 is a schematic diagram of a spray nozzle;

38.FIG. 7 is a schematic diagram for explaining a control of theintegrated control unit;

39.FIG. 8 is a diagram showing a relation between compressor exittemperature and spray rate;

40.FIG. 9 is a diagram showing a relation between load, recirculationrate and mixing gas temperature;

41.FIG. 10 is a diagram showing heat efficiency relative to load;

42.FIG. 11 is a schematic diagram of an embodiment of the presentinvention;

43.FIG. 12 is a schematic diagram of control of an integrated controlunit;

44.FIG. 13 is a schematic diagram of a control line;

45.FIG. 14 is a schematic diagram showing an efficiency characteristicdepending on the atmospheric temperature;

46.FIG. 15 is a schematic diagram showing the atmospheric temperatureand plant output;

47.FIG. 16 is a schematic diagram showing plant efficiency depending onthe atmospheric temperature.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

48.FIG. 1 shows a first embodiment of the present invention. An exhaustgas recirculating type combined plant employing a gas turbine intake airwater spraying system comprises: a compressor (compressor) 1 for suckingand compressing air, a combustion chamber 2 for mixing and burning thecompressed air and fuel; a gas turbine 3 which is driven by combustiongas supplied from the combustion chamber 2; an exhaust heat recoveryboiler 4 for recovering heat of the gas turbine exhaust gas prom the gasturbine 3 so as to generate steam by heat exchange with supplied water;a steam turbine 5 which is driven by the steam generated by the gasturbine exhaust heat recovery boiler 4, a generator 6 coupled with thesteam turbine 5; a recirculating means (pipe) 9 composing arecirculating path for taking out part of the gas turbine exhaust gas ofthe gas turbine 3 and recirculating it up to a compressor intake; and arecirculation amount control means (exhaust gas recirculation amountadjusting valve) 10 for controlling the recirculation amount.

49. Referring to FIG. 1, although the compressor (compressor) 1, gasturbine 3, steam turbine 5 and generator 6 are connected on a same axis,it is permissible to construct so that each turbine may drive eachgenerator.

50. This combined plant further comprises a fuel amount control valve(fuel supply system) 7 for controlling an amount of fuel supplied to thecombustion chamber 2 and an integrated control device 8 for controllingthe fuel amount control valve 7 and the recirculation amount controlmeans 10.

51. According to the first embodiment, spray nozzles 11 for sprayingfine droplets of liquid are disposed in a suction duct 21. A supplywater amount adjusting valve 12 for controlling a spray amount, a watertank 13 for storing water and a water supply pump 14 are disposed on apath for supplying water to the spray nozzles. If the aforementionednozzle requires an air supplying means for obtaining fine liquiddroplets, an air flow adjusting valve 15 is disposed on a suction airsupply path.

52. As for the fine droplets of liquid sprayed, its average dropletdiameter (S.M.D.) is about 10 μm.

53. Generation output of the aforementioned combined plant is operatedby the fuel amount control valve 7 for controlling an amount of fuelloaded on the combustion chamber 2, recirculation amount control means10, spray amount (supply water amount) adjusting valve 12, air flowadjusting valve 15 and determined by adjusting their opening degrees.These operation ends are controlled depending on an operation signalfrom the integrated control device 8. The integrated control device 8receives a load request signal Ld from a central power supply controlroom 16 for the combined plant and controls the entire plant so as toappropriately control air amount, fuel amount and spray amount.

54. An example of the integrated control device will be described withreference to FIG. 2.

55. To control an amount of fuel, first a deviation between a loadrequest signal Ld and an actual load L is obtained by a subtractor AD1and a fuel target signal Fd is obtained by an adjusting device PI1.Then, a deviation between the fuel target signal Fd and actual fuelamount F is obtained by a subtractor AD2 and them the fuel amountcontrol valve 7 is adjusted by the adjusting device PI2 to determine anamount of fuel to be loaded on the combustion chamber. According to thiscontrol, the larger the load, the larger amount of fuel is supplied tothe combustion chamber 2.

56. As for the control of recirculating amount, in a function generatorFG1 which receives the load signal Ld, the smaller the load, the largeroutput signal S1 is obtained. This signal S1 is supplied to theadjusting device PI3 so as to control the recirculation amount controlmeans 10.

57. When an operational value of combustion temperature is input to AD2or AD3 and the AD2 or AD3 makes arithmetic operation, correction iscarried out as required to suppress a deflection of the combustiontemperature. As for the operational value of the combustion temperature,exhaust gas temperature and compressor exit pressure are input to FG2,in which a combustion temperature is calculated based on the gas turbineexhaust gas temperature and pressure and then output.

58. As the load decreases, the recirculation amount increases in termsof supplying speed, preventing a reduction of the combustion temperatureor gas turbine exhaust gas temperature accompanied by a reduction of theload. Preferably, the combustion temperature (gas turbine exhaust gastemperature) can be maintained at a substantially constant levelregardless of the load. In the function generator FG1 of FIG. 1, arecirculation rate of the gas turbine exhaust gas amount is determinedcorresponding to the load. Thus, in the example shown in the samefigure, the output signal S1 of the function generator FG1 can maintainthe gas turbine exhaust gas temperature substantially constantregardless of the load.

59. Like this, by recovering entropy of exhaust gas, reduction ofefficiency at the time of the partial loading can be prevented.

60. In this manner, the gas turbine exhaust gas temperature can bemaintained at a substantially constant level regardless of the load.

61. As for improvement of compressor characteristic, to prevent a dropof the combination temperature at the time of the partial load operationor a reduction of the gas turbine exhaust gas temperature. outside airof the atmospheric temperature is mixed with high temperature gasturbine exhaust gas at the compressor intake so as to obtain intake air.As the load is decreased, the gas turbine exhaust gas amount to berecirculated increases. Then, as the gas turbine exhaust gas increases,naturally the suction air temperature also increases, so thatcorrespondingly, a temperature in the compressor 1 also increases. Asshown in FIG. 3, fluid behavior in the vicinity of compressor vaneschanges. Generally, a peripheral velocity of a moving vane inside thecompressor is constant. If an axial velocity is designed so as to beconstant, an apparent velocity B flowing to the compressor moving vaneis parallel to the vane as shown in (A) . However, if the suction airtemperature rises so that the gas temperature inside the compressor alsorises, an incidence α which is an incidence angle of the apparentvelocity B is increased to increase the axial velocity A′ as shown in(B) Thus, at a compressor rear and in which the temperature rises (e.g.,near the final stage moving vane) flow separation occurs on the vane soas to produce stalling. If this phenomenon is serious, a negativestalling is caused, so that a stable operation of the gas turbinebecomes impossible. Thus, even if the recirculating amount is increasedaccompanied by a reduction of the gas turbine load, there exists a upperlimit of the gas turbine exhaust gas recirculating amount thereby arange of the partial load operation being limited.

62. According to the present embodiment, liquid droplets to be vaporizedin the compressor is introduced into the suction air in which theoutside air of atmospheric temperature and high temperature gas turbineexhaust gas are mixed with each other. As a result, as shown in FIG. 3(C), internal gas of the compressor is cooled so that the axial velocityA′ is reduced at the rear end of the compressor. Consequently, theincidence α is also reduced so that the apparent velocity B becomesparallel to the vane thereby stabilizing the compressor characteristic.Because the internal gas of the compressor can be cooled by vaporizationof liquid droplets inside the compressor, the compressor suction airtemperature can be further increased. That is, because the gas turbineexhaust air recirculation amount can be increased more, the highefficiency partial load operation range can be expanded.

63.FIG. 4 shows a change in incidence relative to the spray amount.Ordinarily, the gas turbine is designed so as to be operated under anatmospheric temperature of 0°C.-50°C., In this interval, thecharacteristic of the compressor is stabilizer regardless of theincidence being changed by a change in the compressor suction airtemperature. However, if the compressor suction air temperature exceedsthis range, the absolute value of the incidence is increased, so thecharacteristic of the compressor becomes unstable. At the worst, apositive stalling (stall) or a negative stalling (choke) may occur.

64. According to the present invention, by introducing the liquiddroplets to be vaporized into the interior of the compressor, theinternal gas inside the compressor is cooled so as to improve theincidence. Referring to FIG. 3, although the incidence is at the lowerlimit of the regular operation range when the suction air temperature is50°C., by spraying liquid droplets at the compressor intake so as tocool the internal gas inside the compressor, the incidence is graduallyrestored, resulting in the incidence being restored to 0 deg with aspray amount of 1.5%. If the spray amount is increased, the problematicpositive stalling (stall) requires an appropriate spray amount to beselected.

65. As described above, introducing the liquid droplets to be vaporizedin the compressor causes a temperature difference between the compressorintake gas and exit gas to be minimized. The intake temperature issubstantially constant and the exit temperature drops or the reductionamount of the exit temperature is made larger than the reduction amountof the intake temperature.

66. Therefore, the recirculation amount can be increased with thecompressor exit temperature being substantially constant.

67. Thus, the recirculation can be attained even at the time of lowpartial load operation.

68. By introducing liquid droplets to be vaporized in the compressor inwhich the aforementioned mixing gas flows so that the liquid dropletsare valorized in the compressor, the efficiency under the partial loadcan be improved as compared to the case of the aforementionedconventional art. The water droplets entering the compressor arevaporized and if the vaporization is completed, the gas in thecompressor is subjected to adiabatic compression. At that time, thespecific heat under a constant pressure of steam is about twice that ofthe mixing gas around a typical temperature (300°C.) in the compressorand therefore, in terms of thermal capacity, if calculated on the basisof the mixing gas, the same effect is produced as when the mixing gashaving a weight about twice that of water droplets to be vaporized actsas an operating liquid. That is, a drop of the mixing gas temperature atthe exit of the compressor has an effect (temperature rise inhibiteffect). The vaporization of water droplets in the compressor like thiscauses the drop of the mixing gas temperature at the exit of thecompressor. An operating power of the compressor is equal to adifference of mixing gas entropy between the intake and exit of thecompressor and the mixing gas entropy is proportional to thetemperature. Thus, if the mixing gas temperature at the exit of thecompressor drops, the required operating power of the compressor can bereduced so that the efficiency can be improved.

69. If the suction air temperature at the intake of the compressor,temperature at the exit of the compressor, combustion temperature andgas turbine exit temperature are assumed to be T₁, T₂, T₃, and T₄respectively, the gas turbine efficiency η is approximately given in afollowing expression.

Expression 1

70. If the compressor exit temperature T₂ drops to T₂′ (<T₂) due to thevaporization by mixing of sprayed water, a second term of the right sideof the above expression becomes smaller, so that it is clear that theefficiency is improved by the water spray. In other words, although thethermal energy Cp (T₄−T₁) thrown out of the gas turbine (a heat engine)does not change largely between before and after the application of thepresent invention, the fuel energy Cp (T₃−T₂′) loaded is increased by Cp(T₁−T₂′) or a reduction amount of the compressor work when applying thepresent invention. Because the reduction amount of the compressor workis equal to an increased output, this increase of the fuel contributessubstantially all to an increase of the output of the gas turbine. Thatis, the increased output attains a heat efficiency of 100%. Therefore,the heat efficiency of the gas turbine can be improved. Because thecombustion temperature is maintained at a constant level, the heatefficiency of bottoming cycle is the same as before the presentinvention has been applied. Therefore, the heat efficiency of thecombined cycle total can be improved.

71. Only reducing the mixing gas temperature introduced into thecompressor may slightly improve the characteristic of the compressor asshown in FIG. 3 in a limited manner.

72. Further, under a low partial load operation, the intake air iscooled so that the weight flow rate of the intake air introduced intothe compressor 1 is increased, resulting in the possibility of aincrease of the load of the gas turbine to be driven under a low load.

73. If the diameter of the sprayed liquid droplet is large, it collideswith the vane or casing of the compressor 1 so that it is vaporized byreceiving a heat from the metal. As a result, the temperature reductioneffect of the operating liquid may be obstructed. Thus, the diameter ofthe liquid droplet is desired to be as small as possible from thisviewpoint.

74. The sprayed liquid droplet has a distribution of the diameters ofthe droplets. To prevent a collision of the droplets against the vane orcasing of the compressor 1 or erosion of the vane, the diameter of thesprayed liquid droplets is controlled so as to be 50 μm or below. Tominimize an effect on the vane, the maximum diameter thereof is desiredto be 50 μm or below.

75. Because the smaller the diameter of the droplet, the more uniformlythe liquid droplets can be distributed in flowing air, so that thedistribution of the temperature in the compressor is suppressed, it isdesirable that the Sautor average diameter (S.D.M.) is 30 μm or below.Because the liquid droplets ejected from an infection nozzle has adistribution of grain size, the aforementioned maximum diameter isdifficult to be measured. Thus, for actual use, the measurement of theaforementioned Sautor average diameter (S.D.M.) is applied. Although thediameter of the droplet is desired to be as small as possible, aninjection nozzle for producing a small droplet requires a high precisionproduction technology. Thus, a lower limit allowing technically as smalla droplet as possible is an actual range of the aforementioned diameterthereof. Therefore, from such a viewpoint, for the aforementioned maindroplet diameter, maximum diameter and average diameter, 1 μm is a lowerlimit. Further, the smaller the diameter of the droplets, the moreenergy is consumed for generating such droplets. Thus, considering theenergy to be consumed for generation of the liquid droplets, it ispermissible to determine the aforementioned lower limit. If the dropletsize is a size allowing it to float in the atmosphere so that it is notlikely to drop, generally, the condition of its contact surface isexcellent.

76. A time in which the air passes through the compressor is very short.To vaporize the liquid droplets excellently in this while and intensifythe vaporization efficiency, the Sautor average diameter (S.D.M.) isdesired to be less than 30 μm.

77. Because a high precision production art is required for productionof an injection nozzle capable of generating small droplets, the lowerlimit technically allowing the droplet diameter to be reduced is thelower limit for the aforementioned grain size. For example, such lowerlimit is 1 μm.

78. This is because if the droplet diameter is too large, thevaporization thereof in the compressor is made difficult.

79. An introduction amount of the droplets can be adjusted depending onthe temperature, humidity and an increase of the output. Taking intoaccount an amount of the vaporization of the liquid droplets in aninterval from a spraying point to the compressor intake, more than 2 wt% relative to the intake air weight flow rate can be introduced. Itsupper limit is determined in a range capable of maintaining the functionof the compressor in an excellent condition. For example, it is possibleto determine the upper limit to be 5 wt % such that the introductionrange is below this value.

80. Although the introduction range can be adjusted considering summerseason and dry condition, to further increase the output, it is possibleto introduce at 0.8 wt % or more and 5 wt % or below.

81. It is permissible to additionally dispose the injection nozzle so asto spray the liquid droplets over compression gas.

82. A position of the spray nozzle 11 will be described with referenceto FIG. 6. Here, reference numeral 22 denotes IGV.

83. The spray nozzle is disposed at any position of 11 a-11 d. Theinfection nozzle 11 a is disposed via a predetermined distance from thecompressor exit. However, if a silencer is disposed within the suctionduct 21, it is disposed in the downstream relative thereto. As a result,if it is intended to not only attain high efficiency partial loadoperation but also achieve high efficiency increased output operation,favorably, a part of the liquid droplet is vaporized before it isintroduced into tile compressor and aster it is introduced into thecompressor, it is further vaporized during a flow in the compressor.

84. The spray nozzle 11 b is disposed on an introduction vane providedin the most upstream which is an introduction portion of the compressor,provided at the compressor intake. An air supplying path and watersupplying path are disposed within the same vane. As a result, aresistance by the spray nozzle to the flow is suppressed and the liquiddroplets can be sprayed without providing special space for installationof the nozzle.

85. A spray nozzle 11 c is disposed between the aforementioned guidevane and IGV. This prevents the sprayed liquid droplets from beingvaporized before entering the compressor and the weight flow rate of themixing gas from increasing. From such a viewpoint, it is desirable toinstall the inject on nozzle near the IGV.

86. By disposition of 11 a-11 c, continuous vaporization within thecompressor can be obtained. Further, by vaporizing as much as possibleat a relatively upstream of the compressor, the compressor exhausttemperature can be reduced, so that a rise of the compressor exhausttemperature can be suppressed.

87. An injection nozzle 11 d is disposed at the middle of thecompressor. For fear of the symptom as stalling of the vane of thecompressor is more likely to occur at the vane of the rear end, thisinjection nozzle may be installed at the middle stage of the compressornear the rear end. In this case, the nozzle is installed on a stationaryvane as shown by an enlarged view and a water supplying means and airsupplying means are provided within the vane.

88. The sprayed liquid droplets flowing in the compressor move betweenthe vanes of the compressor along its flow line. In the compressor, theintake air is heated by adiabatic compression, so that the liquiddroplets are vaporized from the surface by this heat and while thediameter thereof is being reduced, transferred to the rear end vane. Inthis process, vaporization latent heat required for vaporization lowersthe temperature of the mixing gas in the compressor because it dependson the mixing gas in the compressor.

89. The spray amount of the aforementioned injection nozzle 11 iscontrolled so as to correspond to a recirculating amount of thecombustion gas. For example, it is controlled so that the spray amountis larger when the recirculating amount is large than when therecirculating amount is small.

90. At the time of the partial load operation of the gas turbine of thecombined plant, the mixing gas composed of the gas turbine exhaust gasthrough the recirculating pipe 9 and air supplied through the suctionduct 21 is introduced to the compressor 1 and in the compressor 1, theaforementioned mixing gas is compressed and discharged.

91. With this condition, the aforementioned fine liquid droplets aresprayed from the aforementioned spray nozzle 11 and introduced into thecompressor, and during a flow in the compressor 1, the liquid dropletsare vaporized.

92. By adjusting the spray amount depending on the recirculating amount,the partial load operation range in which a high efficiency operation isenabled by recirculating the gas turbine exhaust gas can be enlarged ascompared to carrying out only the gas turbine exhaust gas recirculation.

93. It is possible to improve the characteristic of the compressor whichhas been lowered due to a rise of the compressor intake air temperatureaccompanied by an increase of the recirculation amount at the time ofthe partial load operation, particularly of low load operation.

94. A control of the spray amount will be described with reference toFIG. 2.

95. In this control, an output signal S1 which becomes larger as theload decreases in a function generator FG1 receiving the load requestsignal Ld and a combustion temperature signal estimated from gas turbineexhaust gas temperature and compressor output pressure in a functiongenerator FG2 to correct a combustion temperature change in actualoperation are applied to a subtracter AD3 and then a correctionrecirculation rate signal is output from the function generator FG1.This signal is input to the function generator FG3 in which a sprayamount increases as a recirculation amount increases. An output signalS2 of water droplet spray amount relative to the recirculation amount isobtained. This signal S2 and a next gas temperature of the compressoractually measured are applied to a subtractor AD14 and then a correctionspray amount signal of the function generator FG3 is output. This signalis supplied to an adjustor P14 to control a spray amount (supply wateramount) adjusting valve 12. By this control, the spray amount can beadjusted depending on the recirculation rate.

96. It is permissible to open the air flow adjusting valve 15 ifrequired to produce fine droplets. FIG. 5 indicates a control line ofthe spray rate relative to the recirculation rate assuming that the gasturbine exhaust temperature is constant. The spray rate increasessubstantially linearly relative to the recirculation rate.

97. Although the incidence of the vane in the compressor is changed bythe recirculating operation as described before, it can be returned to astate before exhaust gas recirculation by control of the aforementionedcontrol line. For example, at the atmospheric temperature of 15°C., whenthe recirculation amount is 10% on exhaust gas weight flow basis, thespray amount (on outside air weight basis) is about 3% and when therecirculation amount is 20%, the spray amount is about 5.5%.

98.FIG. 9 indicates a relation between mixing gas intake temperature andrecirculation rate relative to each load. The mixing gas (volumetricflow rate) sucked into the compressor 1 is constant regardless of theload because the gas turbine 3 is rotating at a constant speed. As theload drops, the gas turbine exhaust gas recirculation amount increases,so that correspondingly the compressor intake air temperature rises. Onthe contrary, if the recirculation amount increases so that the mixinggas intake temperature rises, the gas turbine output drops owing to thedecrease of the compressor intake suction weight flow rate. In a plainrecirculation gas turbine of the conventional art, if stalling or thelike on the vane of the last stage is considered, the upper limit of thecompressor intake air is 50° C. and therefore the recirculation amountis restricted so that the gas turbine output reduction is alsorestricted. However, according to the present embodiment, spraying fineliquid droplets at the compressor intake so as to cool the compressorinternal gas, liquid behavior in the vicinity of the compressor vane isimproved. Thus, the gas turbine exhaust gas recirculation amount can beincreased so that operation at a lower load is enabled and further ahigher efficiency partial load operation is enabled. Although thetemperature of the compression air coming out of the compressor 1 islowered due to the vaporization of water droplets in the compressor, thecombustion temperature can be maintained at a constant level byincreasing a fuel loading amount. Next, the combustion gas works in aprocess of its adiabatic expansion in the gas turbine 3. Because a partof the combustion gas is consumed for driving the compressor 1 andgenerator 6, met output thereof corresponds to that difference.

99. The part of the gas turbine exhaust gas from the gas turbine 3recirculates through the recirculating means 9 and control means(exhaust gas recirculation amount adjusting valve) 10 as a part of theintake air in the compressor 1. In the gas turbine exhaust heat recoveryboiler 4, high pressure steam is generated and this steam drives thesteam turbine 5 and generator 6 to generate power.

100.FIG. 10 shows a comparison of efficiency drop due to respectiveloads in the combined cycle with efficiency drop in ordinary combinedcycle, exhaust gas recirculation type combined cycle and the presentembodiment. Although as regards the cycle heat efficiency of theordinary combined cycle, efficiency drop in a range up to 90% load inwhich combustion temperature constant operation is carried out is not solarge, the combustion temperature drops at an operation having a lessthan 90% load. Therefore the efficiency drops rapidly, so that at the25% load which is a load determined by a restriction on the bottomingside, the efficiency drops in terms of a relative value by about 40%.The combustion temperature constant operation by the aforementioned IGVor the like has a range slightly different depending on machine.However, in most cases, the efficiency drop is up to 80% even if it issmall. Although in the gas turbine exhaust gas recirculation typecombined cycle, its cycle heat efficiency drop is smaller than ordinarycombined cycle, it cannot be operated at more than 65% load due torestriction of the compressor intake air temperature. On the contrary,according to the present invention, by cooling the internal gas in thecompressor, the compressor driving power drops and its output increases,so that the heat efficiency is improved. As a result, the efficiencydrop relative to each load is further reduced. Therefore, as compared tothe gas turbine exhaust gas recirculation type combined cycle, a lowerload operation is enabled and theoretically, the operation is enabled upto about 30% load in which oxygen concentration in the gas turbineexhaust gas is zero, The efficiency drop is about 10%.

101. A lower limit is preferred to be determined depending on setting ofthe apparatus, and generally, it is considered that in most cases, therecirculation is carried out up to at least 50% load.

102. Although FIG. 10 considers operation by control by IGV or the likein a range in which combined cycle load is 100-90% or 80%, the presentinvention is not restricted to this example, it is permissible tocontrol the recirculation amount correspondingly if the load descendsfrom 100%.

103. To increase the recirculation amount as the load decreases,assuming that the combustion temperature is 1430°C. and the compressorexit temperature is 370°C. in order to prevent the compressor exittemperature from exceeding 370°C., the compressor intake temperature is150°C. when the combined cycle load is 74%, 112°C. when 50% and 240°C.when 30%. According to the present embodiment, by reducing thecompressor exit temperature by introducing liquid droplets to bevaporized in the compressor, inconveniences which may occur at the rearend of the compressor can be avoided. Thus, by raising the recirculationrate by controlling the spray amount of the liquid droplets to bevaporized in the compressor, it is possible to control so that thetemperature of the mixing gas at the compressor intake rises. Further,the recirculation amount can be increased as compared to a plainrecirculation plant, so that the recirculation amount can be increasedeven in low partial load operation range.

104. Further according to the present embodiment, in a combined plantload range of at least 50-80%, it is possible to control so that theaforementioned spray amount is increased as the recirculation amount isincreased and that the recirculation amount is continuously increased asshe load is decreased.

105. Further, by controlling the aforementioned recirculation amountcorresponding to the load so as to suppress a deflection of thecombustion temperature in the combustion chamber in a combined plantload range of at least 50%-80% (for example, controlling so that therecirculation amount is increased as the load is decreased) andintroducing the liquid droplets into the compressor, it is possible tosuppress a temperature rise of the compression air at the compressorexit.

106. Following control can be carried out in the integrated controldevice 8.

107. The aforementioned recirculation amount and aforementioned liquiddroplet spray amount are controlled corresponding to the load so as tosuppress a deflection of the combustion temperature of the combustionchamber in a combined plant load range of 50%-80%.

108. As the load decreases, the recirculation amount is increased andthe spray amount is also increased so as to suppress a drop of thecombustion temperature and keep it high. As a result, a high efficiencyoperation is enable in a wide range of the partial load.

109. Further, to suppress a deflection of the combustion temperature ofthe combustion chamber in a combined cycle load range of 50%-80%, theaforementioned recirculation amount is controlled corresponding to theload and by introducing the liquid droplets into the compressor, a riseof the temperature of the compression air at the compressor exit issuppressed. Because the compressor exit temperature rises as therecirculation amount is increased, the liquid droplets are introducedinto the compressor and vaporized therein so that that temperature ismaintained in an allowable range.

110. Further, the gas turbine exhaust gas amount to be returned to thecompressor intake is adjusted corresponding to a change of the load inthe aforementioned combined cycle and the aforementioned recirculationamount is controlled corresponding to the load to suppress a deflectionof the combustion temperature of the combustion chamber in a combinedplant load range of 50%-80% thereby controlling the aforementioned sprayamount to be vaporized during a flow in the compressor. In this process,the recirculation amount is so controlled as to be continuouslyincreased as the load lowers. Although if the recirculation amount is socontrolled as to be increased as the load lowers, there is produced anupper limit in the increase amount of the recirculation amount for thereason of the compressor or the like, the introduction amount of theliquid droplets to be vaporized in the compressor is adjusted such thatthe introduction amount of the liquid droplets is increased as the loadlowers. As a result, as the load lowers in a wide range of the partialload, the recirculation amount can be continuously increased.

111. Because the aforementioned upper limit is a upper limit load forcarrying out the recirculation, if the recirculation is carried out whenthe load drops from 100%, the aforementioned upper limit range isexpanded. Further, because the lower limit is determined depending onsetting of the apparatus, it is possible to so control as to increasethe recirculation amount in a wider range.

112. A second embodiment will be described with reference to FIG. 1 andother diagrams. Its basic structure is the same as the first embodiment.Although the spray amount is controlled depending on the gas turbineexhaust gas recirculation amount in the first embodiment, according tothe present embodiment, the spray amount control method differs in thatthe spray amount is controlled depending on a gas temperature measuredat the compressor exit although the gas turbine exhaust gasrecirculation amount control is the same as the first embodiment.Although the combined plant apparatus structure is the same as the firstembodiment, a means for measuring a compressor exit gas temperature andinputting this signal into the integrated control device 8 has beenadded as a spray amount controlling means. FIG. 7 shows an integratedcontrol device 8 of the present embodiment. According to the presentembodiment, as shown in FIG. 7, a measured compressor exit gastemperature is input to the function generator FG3 and then a sprayamount is calculated so as to suppress a deflection of the compressorexit gas temperature before the gas turbine exhaust gas is recirculatedor preferably so that the temperature is constant. It is so controlledso that the spray amount is increased as the exit temperature rises. Bymeans of the adjuster IP4 based on the obtained spray amount signal, thespray amount (supply water amount) adjusting valve 12 is controlled. Onthe other hand, because the combustion temperature may be changed byspraying, the fuel flow rate of a case in which the liquid droplets aresprayed is correctively controlled by applying a spray amount signal toa fuel flow rate signal obtained from the load request signal Ld andactual load L, thereby achieving a constant combustion temperature. Asan example, FIG. 8 shows a control line for calculating a compressorexit gas temperature before the gas turbine exhaust gas recirculationfrom a compressor exit gas temperature when the atmospheric temperatureis 15° C. Although the compressor exit gas temperature is about 450° C.when the gas turbine exhaust gas recirculation amount is 10%, bycarrying out about 2.5% spray at the compressor intake, the compressorexit gas temperature constant operation before carrying out the gasturbine exhaust gas recirculation is made possible. Further because thecompressor exit gas temperature is changed depending on a change of theatmospheric temperature even if the gas turbine exhaust gasrecirculation amount is constant, it is desirable that the control linecontains the atmospheric temperature as a parameter. Thus, an operationnot following a minute change of the output or change in the temperatureis enabled, so that the operation control is facilitated.

113. Because a temperature of the rear end of the compressor which is acause for inconvenience of compression is directly reflected, a higherprecision operation is enabled.

114. A third embodiment will be described with reference to FIG. 1 andother diagrams. Its basic structure is the same as the structure of thefirst embodiment.

115. A feature of the present embodiment exists in that a detection unitfor detecting a mixing gas temperature at the compressor intake isprovided and the spray amount is controlled depending on a temperatureprovided by that temperature detection unit.

116. For example, it is so controlled that when the temperature of themixing gas entering the compressor is high rather than low, more liquiddroplets are sprayed by the integrated control device S. Further, thespray amount is controlled so as to obtain the compressor exittemperature before exhaust gas recirculation.

117. As a result, even at a low partial load operation time, highefficiency operation is enabled.

118. A fourth embodiment will be described with reference to FIG. 1 andother diagrams. Its basic structure is the same as that of the firstembodiment.

119. A feature of the present embodiment exists in that the spray amountis controlled by the integrated control device 8 according to a signalfrom a combined cycle plant load measuring apparatus.

120. For example, it is so controlled that more liquid droplets aresprayed when the load is low rather than high.

121. As a result, at a low partial load operation time, a highefficiency operation is enabled.

122. The load is often measured on regular operation as well and can becontrolled easily because such a signal is available.

123. A fifth embodiment will be described with reference to FIG. 1 andother diagrams.

124. Its basic structure is the same that of the first embodiment. Apoint of the present embodiment is a gas turbine apparatus not providedwith a exhaust heat recovery boiler 4 supplied with exhaust gas from thegas turbine 3 and a steam turbine supplied with steam generated in thegas turbine exhaust heat recovery boiler 4.

125. As described in the aforementioned first embodiments, there isprovided a spray unit for introducing liquid droplets in the compressorin which the mixing gas comprising gas turbine exhaust gas passingthrough the aforementioned recirculation path and air flows so as tovaporize the introduced liquid droplets during a flow in the compressor.As a result, the amount of the gas turbine exhaust gas to be returned tothe compressor is adjusted corresponding to the load change of theaforementioned combined cycle plant. The liquid droplets are sprayedfrom the spray unit into the compressor in which the mixing gascomprising gas turbine exhaust gas passing through the aforementionedrecirculation path and air flows so as to vaporize the introduced liquiddroplets during a flow in the compressor.

126. Additionally, a spray amount control unit for controlling a sprayamount corresponding to the aforementioned recirculation amount is alsoprovided. Corresponding to the load on the combined cycle plant, it isso controlled as to spray more when the load is low rather than high.

127. Further, the spray amount is controlled corresponding to a changeof the temperature of the mixing gas to be introduced to a compressorintake. The spray amount is so controlled as to be more when the mixinggas temperature is high rather than low.

128. As a result, as described above, the temperature of the internalgas in the compressor can be reduced so that the characteristic of thecompressor can be improved. Thus, the gas turbine exhaust gasrecirculation amount can be increased so that the partial load operationrange can be expanded. Further, by an effect of water droplet spray intocompressor intake air, the heat efficiency can be improved higher thanthe gas turbine exhaust gas recirculation type gas turbine apparatus.

129. A sixth embodiment of the present invention will be described withreference to FIGS. 11-16. In the sixth embodiment, the spray amount andrecirculation amount are controlled depending on a temperature ofexhaust gas to be introduced to the compressor.

130.FIG. 11 shows a schematic view of this embodiment. Basically, thisis of the same structure as the schematic view of the first embodiment.In this embodiment, recirculating exhaust gas is introduced from adownstream side of the gas turbine exhaust heat recovery boiler 4.

131. Although the pipe 9 for fetching out a part of exhaust gas of thegas turbine 3 may be provided at any place of the gas turbine exhaustheat recovery boiler, exhaust heat recovery boiler intake portion andoutlet portion, it should be provided at the gas turbine exhaust heatrecovery boiler outlet portion like this embodiment so as to makeeffective use of heat in the gas turbine exhaust gas. The operation endsinclude a fuel amount control valve 7 for controlling the fuel amount tobe charged on the combustion chamber 2, a recirculation amount controlmeans 10, a spray amount adjusting valve 12 and air flow amountadjusting valve 15 and these operation ends are controlled depending onan operation signal dispatched from an integrated control unit 8. Suchan operation enables to control the power generation efficiency of thecombined plant. A signal of a temperature detection unit 18 fordetecting the temperature of air to be supplied to the compressor istransmitted to the integrated control unit. Preferably, a signal of thehumidity detection unit 19 is transmitted. The temperature detectionunit 18 and humidity detection unit 19 can be provided at a convergingportion of the recirculation exhaust gas or in the upstream of the spraynozzle 11. The entire plant is controlled by an instruction from theintegrated control unit 8 so as to control the recirculation amount,fuel amount, air amount and water spray amount appropriately. Forexample, a compressor intake temperature is inputted to raise plantefficiency so that the plant load is controlled so as to be constant.

132.FIG. 12 shows an example of the control mechanism of the integratedcontrol unit. First, a difference between a load request signal Ld andactual load L is obtained by a subtractor AD1 and then a fuel amountobject signal Fd is obtained by an adjuster PI1. Next, a differencebetween the fuel amount object signal Fd and actual fuel amount F isobtained by the subtractor AD2 and a fuel amount control valve 7 isadjusted by an adjuster PI2 so as to determine an amount of fuel to becharged on the combustion chamber. The fuel amount can be controlled inthis manner. For example, this control is capable of increasing theamount of fuel to be charged on the combustion chamber 2 as the loadincreases. According to a compressor intake temperature, preferablyadditionally a compressor intake humidity, an instruction signal S1 onthe recirculation amount is dispatched by a function generator 3 (FG12).This signal is supplied to an adjuster P13 so as to control therecirculation control means 10. Further the function generator 3 (FG12)generates an instruction signal S2 on the spray amount from a spraynozzle 11. This signal is supplied to an adjuster P14 and controls asupply water amount adjusting valve 12 and an air flow adjusting valve15 so as to control a spray amount of droplet from the spray nozzle 11.It is favorable to estimate a combustion temperature from the gasturbine exhaust gas temperature and compressor outlet pressure by meansof a function generator 4 (FG12) and apply this value to the subtractorAD2 to carry out corrective control of the fuel amount. When a changeoccurs in the compressor intake temperature or external air temperature,the fuel is adjusted corresponding to that change thereby suppressing achange in combustion temperature so as to make the combustiontemperature constant. Although keeping the combustion temperatureconstant is important to realize a high efficient plant operation, thereis a possibility that the combustion temperature may change in actualoperation. Therefore, if the change in the combustion temperature iscontrolled based on an actual combustion temperature estimated from theactual exhaust gas temperature of a gas turbine and compressor dischargepressure, it is possible to carry out the operation while suppressing adrop of the combustion temperature at the time of water spray orrecirculation. This prevents a drop of efficiency due to a decrease ofthe fuel temperature.

133. Further, it is desirable to obtain a difference between the loadrequest signal Ld and actual load L by the subtractor AD1 and correct anoutput of the function generator 3. This contributes to making the loadconstant.

134. It is desirable to realize an optimum plant efficient operationbased on the output of the function generator 3.

135. Because the plant efficiency may change in actual operation, it isdesirable to calculate a difference between a requested plant efficiencyηd and actual plant efficiency η by means of the subtractor AD5 andapply an output of the subtractor AD5 to the subtractors AD3, AD4 so asto correct an output of the function generator 1. As a result, a highefficiency operation can be achieved even in actual operation.

136. The function generator 3 calculates a combustion temperatureaccording to a signal from the gas turbine exhaust gas temperaturedetector 24 and a signal from a compressor discharged air temperaturedetector 23 and dispatches a signal to the AD2. For example, it ispossible to calculate so that the combustion temperature is higher whenthe gas turbine exhaust gas temperature is high than when it is low orthe same when the compressor discharge pressure is high than when it islow.

137. A numeral value corresponding to the combustion temperature can beoutputted by other means. The function generator 4 controls a sprayamount of a spray nozzle 11 based on a compressor intake temperature.Further, it controls the recirculation amount. The spray amount and thelike is preferred to be corrected based on the compressor intakehumidity. The spray amount (or a limit value of the spray amount)increases as the temperature rises, so that the spray amount (or a limitvalue of the spray amount) cam be adjusted so as to be larger when thehumidity is low than when it is high.

138. When a detected temperature of air supplied to the compressor is ina set first temperature region, the recirculation is carried out and thespray of droplets from the spray unit is stopped. If the detectedtemperature is in a second temperature region which is higher than thefirst temperature region, the recirculation is stopped and the spray ofthe droplets from the spray unit is stopped. If the detected temperatureis in a third temperature region which is higher than the secondtemperature region, the recirculation is stopped and the spray unit iscontrolled to spray the droplets. It is desirable to set a upper limitand lower limit of a region in which a high combined plant efficiency isensured, so that they are set to a change temperature between the firsttemperature region and second temperature region and a changetemperature between the second temperature region and third temperatureregion. It is desirable to set the aforementioned respectivetemperatures from a range between 15° C. and 22° C. which ensures a highcombined plant efficiency. If some plant deviates from this region, itis desirable to set these values depending on the plant.

139. By monitoring the compressor intake temperature, the recirculationamount and water spray amount are controlled so as to reach such acompressor intake temperature allowing the plant efficiency to bemaximized and realize a constant load on the plant at all times. In thecase of the first temperature region, for example, if the compressorintake temperature is lower than an intake air temperature regionallowing the plant efficiency to be high, the function generator FG3 towhich the compressor intake temperature is to be inputted is requestedto dispatch a signal S1 which increases the recirculation rate as theintake temperature decreases.

140. This signal S1 is supplied to the adjuster PI3 so as to control therecirculation control means 10. The signal S1 controls the recirculationamount to a desired output and can be used as a limit value of therecirculation amount.

141. In the case of the second temperature region, the recirculation andthe spray of droplets from the spray nozzle 11 are stopped. In the caseof the third temperature region, for example if the compressor intaketemperature is higher than the intake air temperature which allows theplant efficiency to be high, the function generator PG1 to which thecompressor intake temperature and humidity are to be inputted isrequested to dispatch a signal S2 which increases the spray rate as theintake air temperature rises or the relative humidity lowers.

142. This signal S2 is supplied to the adjuster PI4 so as to control thewater supply amount adjusting valve 12 and air flow amount adjustingvalve 15.

143. As a result, even if the external air temperature changes, thecompressor intake temperature can be kept constant by the recirculationamount control and spray amount control or the change can be suppressedexcellently. Thus, even if the atmospheric temperature changes, thecombined plant can be operated at a high plant efficiency.

144. Because the first temperature region and third temperature regionare provided through the second temperature region, if the atmospherictemperature changes, the control in the second temperature region inwhich the combined plant efficiency is high can be facilitated. Despitea change in the atmospheric temperature, a desired output can beobtained at a high efficiency.

145. Consequently, a high reliability plant unlikely to be affected by atemperature change can be constructed.

146. As the case may be, it is possible to narrow the aforementionedsecond temperature region and set it to a certain temperature. Such acase is favorable for realizing a high efficiency operation.

147. Because the gas turbine exhaust gas recirculation and water dropletspray are switched over across an atmospheric temperature producing ahigh plant efficiency, the plant control is facilitated.

148. The high efficiency operation will be described. The plantefficiency is determined by the plant output (gas turbine output andsteam turbine output) and fuel flow rate.

149.FIG. 14 shows an efficiency characteristic depending on theatmospheric temperature. If the atmospheric temperature drops below anatmospheric temperature allowing the plant efficiency to be maximized,the compressor intake weight flow rate increases. On the other hand,because the combustion temperature is constant, the fuel flow rateincreases so what the gas turbine output also increases.

150. Although the steam cycle is influenced by an increase of the gasturbine exhaust gas flow rate accompanied by an increase of thecompressor intake weight flow rate and a drop of the gas turbine exhaustgas temperature due to a drop of the atmospheric temperature, the steamturbine output is increased because the influence by the gas turbineexhaust gas flow rate is large.

151. However because the increase rate of the steam turbine output issmaller that that of the gas turbine output, the increase rate of theplant output is small so that the plant efficiency is also small.

152. On the other hand, if the atmospheric temperature rises over anatmospheric temperature under which the plant efficiency is maximized,the fuel flow rate decreases with a decrease of the compressor intakeweight flow rate, so that the gas turbine output and steam turbineoutput drop. Particularly because the gas turbine output drop is large,the plant efficiency is reduced.

153.FIG. 15 shows a relation between the atmospheric temperature andplant output. The plant output changes depending on the atmospherictemperature and as the atmospheric temperature lowers, the plant outputincreases as shown by broken line. However, in actual power generationplants, each approved output is specified and therefore it is consideredthat an operation exceeding that limit is not carried out. Therefore, isthe approved output is reached, the approved output constant operationis continued irrespective of the atmospheric temperature as shown by asolid line and at this time, the gas turbine is operated with a partialload. If the atmospheric temperature rises, the gas turbine compressorintake weight flow rate and fuel flow rate are reduced so that the plantoutput drops.

154.FIG. 16 shows a plant efficiency characteristic depending on theatmospheric temperature. In the aforementioned combined plant, if theapproved output constant operation is carried out, the gas turbine isoperated with its partial load, and therefore the plant efficiency isreduced extremely. However, by this embodiment, the gas turbine intaketemperature can be the same as the atmospheric temperature allowing ahigh plant efficiency.

155. For example, with the recirculation rate of 0-40% with respect tothe gas turbine exhaust gas flow rate, the plant efficiency can beimproved by about 0-1.5% in terms of its relative value. If thecompressor intake temperature is higher than the atmospheric temperaturein which the plant efficiency is high, the plant efficiency can beimproved by about 0.1% in terms of the relative value by a spray amount0-0.2% the gas turbine intake flow rate by spraying droplets from thewater spray nozzle 11 to gas turbine intake air. Therefore, if theatmospheric temperature is low, by returning a part of the gas turbineexhaust gas to the compressor intake by the gas turbine exhaust gasrecirculation system, the compressor intake weight flow rate can bereduced so as to reduce the plant output. Therefore, the gas turbine canbe operated at the approved output constant rating without beingoperated with its partial load. Further, if the atmospheric temperatureis high, the plant output can be increased by increasing the compressorintake weight flow rate by the intake air water spray system, so thatthe constant loaded operation can be achieved at a high efficiencywithout depending on the atmospheric temperature. The seventh embodimentwill be described with reference to FIGS. 11-16.

156. Basically, the seventh embodiment is capable of having the samestructure as the sixth embodiment except that: If the detectedtemperature of air supplied to the compressor is in the firsttemperature region under control of the sixth embodiment, theaforementioned recirculation is carried out and the spray of dropletsfrom the spray unit is stopped. If the detected temperature is in thesecond temperature region which is higher than the first temperatureregion, the aforementioned recirculation is carried out and the sprayunit is controlled to spray droplets. If the detected temperature is inthe third temperature region which is higher than the second temperatureregion, the aforementioned recirculation is stopped and the spray unitis controlled to spray droplets.

157. The change temperature between the first temperature region andsecond temperature region, and the change temperature between the secondtemperature region and third temperature region can be set in the sameway as in the sixth embodiment. FIG. 13 shows an example of the controlline.

158. First, in the first temperature region (for example, in a case whenthe compressor intake temperature is lower than such a compressor intaketemperature in which the plant efficiency is maximized), it is socontrolled that the recirculation amount increases as the compressorintake temperature lowers.

159. In the second temperature region (for example, in such atemperature region in which the compressor intake temperature includes acompressor intake temperature allowing the plant efficiency to bemaximized), the gas turbine exhaust gas is recirculated and theaforementioned droplet spray from the water spray nozzle 11 is carriedout. In this embodiment, FIG. 13 shows a case in which the secondtemperature region is more than 19° C. and less than 25° C. Preferably,the second temperature region is divided to a high temperature side anda low temperature side relative to the set value. The set value ispreferred to be determined with respect to such a value in which thecombined plant efficiency is high. For example, it can be set in a rangeof 15° C.-22° C. Further the second temperature region can be set byproviding the set value with an allowance of ±2°C.-±3°C.

160. The aforementioned second temperature region should be set to aregion in which the plant can be operated with stability. Concretely,the compressor intake temperature allowance may be about 5°C.

161. In the aforementioned low temperature region, the recirculationamount is kept constant and the intake air water spray system isstarted. The spray amount (or a limit value of the spray amount) ordroplets from the water spray nozzle is preferred to be set so as tolarger when the temperature is higher. The spray amount can becontrolled to such a compressor intake temperature in which a plantefficiency is increased when the load on the plant is kept constant. Itis possible to so control that the recirculation amount is kept constantuntil the compressor intake temperature reaches a compressor intaketemperature in which the plant efficiency is maximized and the sprayamount increases as the compressor intake temperature rises.

162. In the high temperature region, it is favorable to so control thatwith the spray amount kept constant, the recirculation amount isdecreased when the temperature of air to be supplied to the compressoris high as compared to when it is low.

163. In the third temperature region (for example, in a case when thecompressor intake temperature is higher than a compressor intaketemperature in which the plant efficiency is maximized), therecirculation of the gas turbine exhaust gas is stopped and water issprayed from the water spray nozzle 11. For example, it can be socontrolled that the spray amount increases as the compressor intaketemperature rises.

164. As a result, even if the external air temperature changes, highefficiency constant operation can be achieved.

165. Because there is provided a region in which the recirculation ofthe gas turbine exhaust gas and spray of droplets from the water spraynozzle 11 are carried out even when the external air temperaturechanges, the changeover in the second temperature region can be executedsmoothly.

166. Further, it is possible to suppress changes in the efficiency ofthe plant and output thereof in a temperature region in which the plantefficiency is high. That is, it is possible to suppress a deviation froma desired output by preventing the output change while achieving smoothdroplet spray and recirculation.

167. By forming such a temperature region in which the spray of dropletsand recirculation of the gas turbine exhaust gas are executed in theaforementioned second temperature region or a region in which the waterspray from the water spray nozzle 11 and changeover of the recirculationof the gas turbine exhaust gas are carried out, even if the external airtemperature changes suddenly, the high efficiency operation can becontinued responding quickly to this. Further, this embodiment iscapable of largely contributing to an operation ensuring a highefficiency and suppressing a change in load (preferably, constant loadoperation) even if the external air temperature changes. Particularly,it is possible to easily suppress a change in the spray amount due to achange in the external air temperature and a output change due to achange in the recirculation amount.

168. An eighth embodiment of the present invention will be describedwith reference to FIG. 17.

169. The eighth embodiment includes a carbon dioxide gas condensingmechanism for condensing carbon dioxide so as to reduce carbon dioxide(e.g., CO₂) in the gas turbine exhaust gas and a carbon dioxide gasremoving unit 41 for reducing the concentration of carbon dioxidecontained in the gas turbine exhaust gas, which contains the condensedcarbon dioxide gas.

170. In the gas turbine exhaust gas recirculation plant, by returningthe gas turbine exhaust gas to the intake of the gas turbine so as toachieve recirculation in the gas turbine cycle, the concentration ofcarbon dioxide gas becomes higher than the conventional plant. As therecirculation amount increases, the concentration of the carbon dioxidein the gas turbine exhaust gas becomes higher. As a result, the carbondioxide removing efficiency also rises. When the concentration of oxygenin the gas turbine exhaust gas becomes zero, namely the gas turbineexhaust gas recirculation rate is 75%, the concentration of carbondioxide in the gas turbine exhaust gas becomes about four times ascompared to the conventional plant.

171. Because the performance of the carbon dioxide gas removing unit isparallel to the concentration of carbon dioxide gas, volumetric flowrate and transfer area, if the concentration of carbon dioxide becomesfour times while the performance of the carbon dioxide gas removing unitis the same, the transfer area can be reduced by ¼.

172. For the reason, the carbon dioxide gas can be reduced byintroducing the gas turbine exhaust gas containing the condensed carbondioxide gas to the carbon dioxide gas removing unit 41. Therefore, ascompared to a case when the carbon dioxide gas removing unit is onlyinstalled in the gas turbine plant, the carbon dioxide can be removed ata high efficiency. Further, if the same removing performance as thecarbon dioxide gas removing unit of the conventional plant is ensured,the size of the carbon dioxide gas removing unit can he reduced.

173. Therefore, because the size of the carbon dioxide gas removing unitto be installed on the flow path of the gas turbine exhaust gas can bereduced, the pressure loss can be suppressed thereby contributing to ahigh efficiency operation of the gas turbine.

174. Additionally, in the carbon dioxide gas condensing mechanism, thegas turbine exhaust gas is recirculated so as to run the gas turbineaccording to this embodiment, carbon dioxide gas of a high concentrationis generated and the gas turbine exhaust gas of a high concentration isintroduced to the carbon dioxide gas removing unit. As a result, the gasturbine can be operated at a higher efficiency.

175. Because the carbon dioxide can be removed at a high efficiencywhile achieving a high efficiency operation of the gas turbine, there issuch a basic effect as forming a gas turbine or combined plant takingcare of the environment and gentle to the environment.

176. The spray nozzle 11 is preferred to be run as described in theaforementioned embodiment.

177. Basically the eighth embodiment can possess a structure of thesixth embodiment. The eighth embodiment contains a carbon dioxide gasremoving unit 41 a which is provided on an exhaust gas path 31 as wellas the structure of the sixth embodiment.

178. The gas turbine exhaust gas emitted from the gas turbine 3 suppliedto the upstream of the compressor 1 through a recirculating means 9.Mixing gas comprising air and recirculated exhaust gas is introduced tothe compressor 1 so as to raise the pressure. The mixing gas dischargedfrom the compressor 1 and fuel are introduced to the gas turbine chamber2 and burnt together. As a result, gas turbine exhaust gas having ahigher concentration of carbon dioxide than a plain gas turbine havingno recirculating means is discharged from the gas turbine chamber 2 soas to drive the gas turbine 3. A part of the gas turbine exhaust gashaving a high concentration of carbon dioxide is diverged to therecirculating means 9 and the remainder thereof is introduced to thecarbon dioxide gas removing unit 41 a installed on the gas turbineexhaust gas path 31 in the downstream of the diverging portion so thatthe concentration of the carbon dioxide is reduced. After theconcentration of the carbon dioxide is reduced, the gas turbine exhaustgas is emitted to the air through a stack or the like.

179. As a result, in addition to the aforementioned basic effect, ascompared to a case in which the carbon dioxide gas removing unit 41 ofthe present invention is installed on the gas turbine exhaust gas path32 or recirculation means 9 between the gas turbine and the divergingportion of the recirculating means 9, the carbon dioxide concentrationof the gas turbine exhaust gas to be supplied to the carbon dioxide gasremoving unit 41 can be maintained at a high level. Thus, the carbondioxide can be removed at a high efficiency. Further, in a case when notso a high efficiency is required, the size of the carbon dioxide gasremoving unit 41 can be reduced while ensuring a desired performance.Due to the reduced size, the pressure loss in the gas turbine exhaustgas path can be reduced, thereby contributing to a high efficiencyoperation of the gas turbine. Further, because an amount of the gasturbine exhaust gas to be diverged by the recirculating means 9 andemitted to the air is introduced to the carbon dioxide gas removing unit9, that amount can be smaller than otherwise thereby the pressure lossbeing suppressed from this point of view, contributing to a highefficiency operation of the gas turbine.

180. Even in a case when the recirculation amount is controlled to bedeflected, the control of carbon dioxide to be emitted to the air isfacilitated.

181. To remove the carbon dioxide gas at a high efficiency whileachieving a highly stabilized recirculating operation, it is preferablethat the recirculation amount is lower than 75% the flow rate of the gasturbine exhaust gas.

182. As the carbon dioxide gas removing unit 41, it is possible to useone having a carbon dioxide gas removing performance capable of reducingthe concentration of carbon dioxide to be supplied to the carbon dioxidegas removing unit by 5%-10%. For example, the carbon dioxide gasremoving unit may be one using amine base absorptive agent.

183. In a case when the gas turbine exhaust heat recovery boiler 4 isdisposed in the downstream of the diverging portion of the recirculatingmeans 9, the carbon dioxide gas removing unit is preferred to be locatedin the downstream of the gas turbine exhaust heat recovery boiler fromviewpoints of a more compact structure, material strength and the like.This unit may be disposed within the gas turbine exhaust heat recoveryboiler from viewpoints of simplification of the apparatus on the gasturbine exhaust gas path.

184. A ninth embodiment will he described with reference to FIG. 17.

185. Basically, the ninth embodiment can employ a structure of theeighth embodiment. According to the ninth embodiment, instead of thecarbon dioxide gas removing unit 41 a of the eighth embodiment, a carbondioxide gas removing unit 41 b is installed on the gas turbine exhaustgas path 32 between the gas turbine and the diverging portion to therecirculating means 9.

186. The gas turbine exhaust gas emitted from the gas turbine 3 issupplied to the compressor 1 through the recirculating means 9. Mixinggas comprising air and recirculated exhaust gas is introduced to thecompressor 1 so as to raise the pressure. The mixing gas discharged fromthe compressor 1 and fuel are introduced to the gas turbine chamber 2and burnt together. As a result, gas turbine exhaust gas having a higherconcentration of carbon dioxide than a plain gas turbine having norecirculating means is discharged from the gas turbine chamber 2 so asto drive the gas turbine 3. The gas turbine exhaust gas having a highconcentration of carbon dioxide is introduced to the carbon dioxide gasremoving unit 41 b so as to reduce the concentration of the carbondioxide gas. A part of the gas turbine exhaust gas in which theconcentration of carbon dioxide is reduced is diverged to therecirculating means 9 and the remainder is emitted to the air through astack or the like.

187. In addition to the basic effect of the aforementioned eighthembodiment, as compared to a case when the carbon dioxide gas removingmeans 41 is installed on the recirculating means or exhaust gas path 31,a larger amount of higher concentration carbon dioxide gas can besupplied to the carbon dioxide gas removing unit 41 b. Therefore, thecarbon dioxide gas capture rate per unit area of the carbon dioxide gasremoving unit 41 b is increased, so that the carbon dioxide gas removingefficiency can be improved. If not so high an efficiency is demanded,the size of the carbon dioxide gas removing unit 41 can be reduced whileensuring a desired performance.

188. A tenth embodiment will be described with reference to FIG. 17.

189. Basically, the tenth embodiment can employ a structure of theeighth embodiment. According to the tenth embodiment, instead of thecarbon dioxide gas removing unit 41 a of the eighth embodiment, a carbondioxide gas removing unit 41 c is installed as the recirculating means9.

190. The gas turbine exhaust gas emitted from the gas turbine 3 issupplied to the upstream of the compressor 1 through a recirculatingmeans 9. Mixing gas comprising air and recirculated exhaust gas isintroduced to the compressor 1 so as to raise the pressure. The mixinggas discharged from the compressor 1 and fuel are introduced to the gasturbine chamber 2 and burnt together. As a result, gas turbine exhaustgas having a higher concentration of carbon dioxide than a plain gasturbine having no recirculating means is discharged from the gas turbinechamber 2 so as to drive the gas turbine 3. A part of the gas turbineexhaust gas having a high concentration of carbon dioxide is diverged tothe recirculating means 9 and the remainder thereof is emitted to theair through a stack or the like. The diverged exhaust gas to therecirculating means 9 is introduced to the carbon dioxide gas removingunit 41 b, in which the concentration of the carbon dioxide is reduced.After the concentration of the carbon dioxide is reduced, the gasturbine exhaust gas is supplied to the compressor 1 again.

191. As described above, in addition to the basic effect so the eighthembodiment, it is unnecessary to install the carbon dioxide gas removingunit 41 producing a pressure loss in a path for discharging the gasturbine exhaust gas to the air, thereby contributing to a highefficiency operation of the gas turbine. Further, the carbon dioxide gasremoving unit 41 c can be installed easily as well as when it isadditionally installed on an existing gas turbine plant. Further,because the carbon dioxide gas removing unit 41 c is installedseparately from a system in which the gas turbine exhaust gas alwaysflows, in the gas turbine plant using the recirculating means ifnecessary, the maintenance thereof is facilitated. Even in a case whenthe maintenance work on the carbon dioxide gas removing unit 41 c iscarried out, it is possible to carry out the maintenance work with thegas turbine operation being continued by shutting down the gas turbineexhaust gas flowing into the recirculating line.

192. According to the present invention, it is possible to provide anexhaust gas recirculation type gas turbine apparatus having a widepartial load operation range, which can be efficiently operated.

193. It is further understood by those skilled in the art that theforegoing description is a preferred embodiment of the disclosed deviceand that various changes and modifications may be made in the inventionwithout departing from the spirit and scope thereof.

What is claimed is:
 1. An exhaust gas recirculation type gas turbineapparatus comprising: a compressor for compressing air; a combustionchamber for burning compression air exhausted from said compressor andfuel; a gas turbine driven by gas turbine exhaust gas from saidcombustion chamber; a recirculation path for recirculating a part ofsaid gas turbine exhaust gas to an intake of said compressor; arecirculation amount control unit for adjusting an amount of gas turbineexhaust gas to be returned to the intake of said compressorcorresponding to a change in load of said gas turbine; and a spray unitfor introducing liquid droplets into an interior of said compressor inwhich mixing gas comprising gas turbine exhaust gas passing through saidrecirculation path and air flows so as to vaporize the introduced liquiddroplet during a flow in said compressor.
 2. An exhaust gasrecirculation type gas turbine apparatus comprising: a compressor forcompressing air; a combustion chamber for burning compression airexhausted from said compressor and fuel; a gas turbine driven by gasturbine exhaust gas from said combustion chamber; a recirculation pathfor recirculating a part of said gas turbine exhaust gas to an intake ofsaid compressor; a recirculation amount control unit for adjusting anamount of gas turbine exhaust gas to be returned to the intake of saidcompressor corresponding to a change in load of said gas turbine; and aspray unit for spraying liquid droplets over air supplied to saidcompressor and gas turbine exhaust gas passing through saidrecirculation path so as to introduce the liquid droplets into thecompressor in which said air and said gas turbine exhaust gas flow sothat said introduced liquid droplets are vaporized during a flow in saidcompressor.
 3. An exhaust gas recirculation type gas turbine apparatuscomprising: a compressor for compressing air; a combustion chamber forburning compression air exhausted from said compressor and fuel; a gasturbine driven by gas turbine exhaust gas from said combustion chamber;a recirculation path for recirculating a part of said gas turbineexhaust gas to an intake of said compressor; a recirculation amountcontrol unit for adjusting an amount of gas turbine exhaust gas to bereturned to the intake of said compressor corresponding to a change inload of said gas turbine; and a spray unit for spraying liquid dropletshaving an average diameter of 30 μm or below so as to introduce theliquid droplets into the compressor in which mixing gas comprising gasturbine exhaust gas passing through said recirculation path and airflows, and said spray unit being disposed at the upstream of saidcompressor.
 4. An exhaust gas recirculation type gas turbine apparatuscomprising: a compressor for compressing air; a combustion chamber forburning compression air exhausted from said compressor and fuel; a gasturbine driven by gas turbine exhaust gas from said combustion chamber;a recirculation path for recirculating a part of said gas turbineexhaust gas to an intake of said compressor; a recirculation amountcontrol unit for adjusting an amount of gas turbine exhaust gas to bereturned to the intake of said compressor corresponding to a change inload of said gas turbine; a spray unit for introducing liquid dropletsinto an interior of said compressor in which mixing gas comprising gasturbine exhaust gas passing through said recirculation path and airflows so as to vaporize the introduced liquid droplet during a flow insaid compressor; and a spray amount control unit for controlling a sprayamount of said liquid droplets corresponding to said recirculationamount.
 5. An exhaust gas recirculation type gas turbine apparatuscomprising: a compressor for compressing air; a combustion chamber forburning compression air exhausted from said compressor and fuel; a gasturbine driven by gas turbine exhaust gas from said combustion chamber;a recirculation path for recirculating a part of said gas turbineexhaust gas to an intake of said compressor; a recirculation amountcontrol unit for adjusting an amount of gas turbine exhaust gas to bereturned to the intake of said compressor corresponding to a change inload of said gas turbine; a spray unit for introducing liquid dropletsinto an interior of said compressor in which mixing gas comprising gasturbine exhaust gas passing through said recirculation path and airflows so as to vaporize the introduced liquid droplet during a flow insaid compressor; and a spray amount control unit for controlling a sprayamount of said liquid droplets corresponding to a change in load of thegas turbine apparatus.
 6. An exhaust gas recirculation type gas turbineapparatus comprising: a compressor for compressing air; a combustionchamber for burning compression air exhausted from said compressor andfuel; a gas turbine driven by gas turbine exhaust gas from saidcombustion chamber; a recirculation path for recirculating a part ofsaid gas turbine exhaust gas to an intake of said compressor; arecirculation amount control unit for adjusting an amount of gas turbineexhaust gas to be returned to the intake of said compressorcorresponding to a change in load of said gas turbine; a spray unit forintroducing liquid droplets into an interior of said compressor in whichmixing gas comprising gas turbine exhaust gas passing through saidrecirculation path and air flows so as to vaporize the introduced liquiddroplet during a flow in said compressor; and a spray amount controlunit for controlling a spray amount of said liquid dropletscorresponding to a change in the temperature of mixing gas to beintroduced into said compressor.
 7. An exhaust gas recirculation typegas turbine comprising: a compressor for compressing air; a combustionchamber for burning compression air exhausted from said compressor andfuel; a gas turbine driven by gas turbine exhaust gas from sadcombustion chamber; a recirculation path for recirculating a part ofsaid gas turbine exhaust gas to an intake of said compressor; arecirculation amount control unit for adjusting an amount of gas turbineexhaust gas to be returned to the intake of said compressorcorresponding to a change in load of said gas turbine; a spray unit forintroducing liquid droplets into an interior of said compressor in whichmixing gas comprising gas turbine exhaust gas passing through saidrecirculation path and air flows so as to vaporize the introduced liquiddroplet during a flow in said compressor; and a control unit forcontrolling said recirculation amount and a spray amount of said liquiddroplets corresponding to the load so as to suppress a change in thecombustion temperature of the combustion chamber under a gas turbineload of within the range of 50%-80%.
 8. An exhaust gas recirculationtype combined cycle plant apparatus comprising: a compressor forcompressing air; a combustion chamber for burning compression airexhausted from said compressor and fuel; a gas turbine driven by gasturbine exhaust gas from said combustion chamber; an exhaust heatrecovery boiler 4 for recovering heat of the exhaust gas from the gasturbine 3 so as to generate steam by heat exchange with supplied water;a steam turbine 5 which is driven by the steam generated by the exhaustheat recovery boiler 4; a recirculation path for recirculating a part ofsaid gas turbine exhaust gas to an intake of said compressor; arecirculation amount control unit for adjusting an amount of gas turbineexhaust gas to be returned to the intake of said compressorcorresponding to a change in load of said gas turbine; a spray unit forintroducing liquid droplets into an interior of said compressor in whichmixing gas comprising gas turbine exhaust gas passing through saidrecirculation path and air flows so as to vaporize the introduced liquiddroplet during a flow in said compressor; and a control unit forcontrolling said spray amount in a combined cycle plant load within therange of 50%-80% so that the recirculation amount is continuouslyincreased as the load decreases.
 9. An exhaust gas recirculation typegas turbine apparatus comprising: a compressor for compressing air; acombustion chamber for burning compression air exhausted from saidcompressor and fuel; a gas turbine driven by gas turbine exhaust gasfrom said combustion chamber; a recirculation path for recirculating apart of said gas turbine exhaust gas to an intake of said compressor; aspray unit for introducing liquid droplets into an interior of saidcompressor in which mixing gas comprising gas turbine exhaust gaspassing through said recirculation path and air flows so as to vaporizethe introduced liquid droplet during a flow in said compressor; atemperature detector for detecting a temperature of air supplied to thecompressor; and a control unit for controlling so that in the case of afirst temperature region in which said detected temperature is set, saidrecirculation is executed and spray of droplets from said spray unit isstopped, in the case of a second temperature region which is higher thensaid first temperature region, said recirculation is executed and thespray of droplets from said spray unit is executed and in the case of athird temperature region which is higher than said second temperatureregion, said recirculation is stopped and the spray of droplets fromsaid spray unit is executed.
 10. An exhaust gas recirculation type gasturbine apparatus comprising: a compressor for compressing air; acombustion chamber for burning compression air exhausted from saidcompressor and fuel; a gas turbine driven by gas turbine exhaust gasfrom said combustion chamber; a recirculation path for recirculating apart of said gas turbine exhaust gas to an intake of said compressor; aspray unit for introducing liquid droplets into an interior of saidcompressor in which mixing gas comprising gas turbine exhaust gaspassing through said recirculation path and air flows so as to vaporizethe introduced liquid droplet during a flow in said compressor; atemperature detector for detecting a temperature of air supplied to thecompressor; and a control unit for controlling so that in the case of afirst temperature region in which said detected temperature is set, saidrecirculation is executed and spray of droplets from said spray unit isstopped, in the case of a second temperature region which is higher thansaid first temperature region, said recirculation is stopped and thespray of droplets from said spray unit is stopped and in the case of athird temperature region which is higher than said second temperatureregion, said recirculation is stopped and the spray of droplets fromsaid spray unit is executed.
 11. An exhaust gas recirculation type gasturbine apparatus according to claim 1 further comprising a control unitfor controlling a spray amount of droplet from said spray unit dependingon a humidity of air supplied to the compressor.
 12. An exhaust gasrecirculation type gas turbine apparatus comprising: a compressor forcompressing air; a gas turbine chamber for burning compression airexhausted from said compressor and fuel; a gas turbine driven by gasturbine exhaust gas from said gas turbine chamber; a recirculation pathfor recirculating a part of said gas turbine exhaust gas to an intake ofsaid compressor; and a carbon dioxide gas removing unit installed in aflow path of gas turbine exhaust gas for reducing the concentration ofcarbon dioxide gas in the gas turbine exhaust gas discharged after aircontaining the recirculated exhaust gas is introduced to said gasturbine chamber.
 13. An exhaust gas recirculation type gas turbineapparatus according to claim 12 wherein said carbon dioxide gas removingmeans is disposed between a diverging portion of said recirculation pathof said gas turbine exhaust gas path and an emitting portion foremitting said gas turbine exhaust gas to the air.
 14. An exhaust gasrecirculation type gas turbine apparatus according to claim 12 whereinsaid carbon dioxide gas removing means is disposed between said gasturbine of said gas turbine exhaust gas path and a diverging portion ofsaid recirculating path.
 15. An exhaust gas recirculation type gasturbine apparatus according to claim 12 wherein said carbon dioxide gasremoving means is disposed on said recirculating path.
 16. An operationmethod of exhaust gas recirculation type gas turbine apparatuscomprising the steps of: compressing air in a compressor; burning thecompressed air and fuel; driving a gas turbine with gas turbine exhaustgas from said combustion chamber; recirculating a part of said gasturbine exhaust gas to an intake of said compressor through arecirculation path; adjusting an amount of gas turbine exhaust gas to bereturned to the intake of said compressor corresponding to a change inthe load of said gas turbine; and introducing liquid droplets into thecompressor in which mixing gas comprising gas turbine exhaust gaspassing through said recirculation path and air flows by spraying theliquid droplets from a spray unit so that the introduced liquid dropletsare vaporized during a flow in said compressor.
 17. An operation methodof exhaust gas recirculation type gas turbine apparatus comprising thesteps of: compressing air in a compressor; burning the compressed airand fuel; driving a gas turbine with gas turbine exhaust gas from saidcombustion chamber; recirculating a part of said exhaust gas to anintake of said compressor through a recirculation path; adjusting anamount of gas turbine exhaust gas to be returned to the intake of saidcompressor corresponding to a change in the load of said gas turbine;controlling said recirculation amount corresponding to the load so as tosuppress a change in the combustion temperature of the combustionchamber in a gas turbine load within the range of 50%-80%; andintroducing liquid droplets into the compressor so as to suppress a riseof the temperature of the compression air at an exit of the compressor.18. An operation method of exhaust gas recirculation type combined cycleplant comprising the steps of: compressing air in a compressor; burningthe compressed air and fuel; driving a gas turbine with gas turbineexhaust gas from said combustion chamber; a exhaust heat recovery boiler4 or recovering heat of the exhaust gas from the gas turbine 3 so as togenerate steam by heat exchange with supplied water; a steam turbine 5which is driven by the steam generated by the exhaust heat recoveryboiler 4; recirculating a part of said gas turbine exhaust gas to anintake of said compressor through a recirculation path; adjusting anamount of gas turbine exhaust gas to be returned to the intake of saidcompressor corresponding to a change in the load of said gas turbine;controlling said recirculation amount corresponding to the load so as tosuppress a change in the combustion temperature of the combustionchamber in a combined cycle plant load within the range of 50%-80%; andcontrolling said spray amount of the liquid droplets to be vaporizedduring a flow in said compressor so that the recirculation amount iscontinuously increased as the load decreases.
 19. A running method of anexhaust gas recirculation type turbine apparatus comprising the stepsof: compressing air by a compressor; burning the compressed air and fuelin a combustion chamber; driving a gas turbine by gas turbine exhaustgas from said combustion chamber; recirculating a part of said exhaustgas to an intake of said compressor through a recirculation path;spraying liquid droplets from a spray unit to introduce the liquiddroplets into the compressor in which mixing gas comprising gas turbineexhaust gas and air flows through said recirculation path so as tovaporize the introduced liquid droplet during a flow in said compressor;detecting a temperature of air supplied to the compressor; andcontrolling so that in the case of a first temperature region in whichsaid detected temperature is set, said recirculation is executed andsaid spray is stopped, in the case of a second temperature region whichis higher than said first temperature region, said recirculation isexecuted and said spray is executed and in the case of a thirdtemperature region which is higher than said second temperature region,said recirculation is stopped and said spray is executed.
 20. A runningmethod of an exhaust gas recirculation type turbine apparatus comprisingthe steps of: compressing air by a compressor; burning the compressedair and fuel in a combustion chamber; driving a gas turbine by gasturbine exhaust gas from said combustion chamber; recirculating a partof said exhaust gas to an intake of said compressor through arecirculation path; spraying liquid droplets from a spray unit tointroduce the liquid droplets into the compressor in which mixing gascomprising gas turbine exhaust gas and air flows through saidrecirculation path so as to vaporize the introduced liquid dropletduring a flow in said compressor; detecting a temperature of airsupplied to the compressor; and controlling so that in the case of afirst temperature region in which said detected temperature is set, saidrecirculation is executed and said spray is stopped, in the case of asecond temperature region which is higher than said first temperatureregion, said recirculation as stopped and said spray is stopped and inthe case of a third temperature region which is higher than said secondtemperature region, said recirculation is stopped and said spray isexecuted.
 21. An operation method of exhaust gas recirculation typecombined cycle plant comprising the steps of: compressing air in acompressor; burning the compressed air and fuel in a gas turbinechamber; driving a gas turbine with gas turbine exhaust gas from saidgas turbine chamber; recirculating a part of said gas turbine exhaustgas to an intake of said compressor through a recirculating path; andburning fuel with air containing said gas turbine exhaust gasrecirculated in said gas turbine chamber so as to reduce theconcentration of carbon dioxide gas in gas turbine exhaust gasdischarged after the burning.